Giant Tun Snail

Overview

The Giant Tun Snail (Tonna galea) is a large, predatory marine gastropod recognized by its distinctive, barrel-shaped shell. It is widely distributed across tropical and subtropical waters, including the Atlantic Ocean and the Mediterranean Sea, where it typically inhabits sandy or muddy seafloors.

Distribution & habitat

This species is found in the Atlantic Ocean, ranging from North Carolina through the Caribbean to Brazil, and from Portugal to northwestern Africa. It is also present in the Mediterranean Sea. These snails prefer soft, benthic substrates like sand or mud, often in areas colonized by marine plants, where they can remain partially buried during the day.

Appearance

The shell is globose and lightweight with a low spire, resembling a large cask or barrel. It features approximately 20 strong, flat spiral ribs separated by narrow furrows. The shell color ranges from whitish-brown to tan, often with a darker aperture. While average adults measure between 13 and 20 cm, exceptional specimens can exceed 30 cm in length.

Biology & behavior

Tonna galea is a nocturnal, slow-moving predator. During daylight hours, it typically hides by burying itself in the substrate, sometimes leaving a small hump visible on the seafloor. It emerges at night to forage. A unique biological feature of this snail is its ability to produce secretions containing sulfuric acid, which it uses to subdue prey.

Feeding

As a carnivore, the Giant Tun Snail primarily hunts echinoderms, such as sea cucumbers, sea stars, and sea urchins. It uses a long, extensible proboscis to capture and envelop its prey, often consuming organisms that are larger than its own mouth opening.